SRAM 2013 Red Aeroglide Rear Derailleur Medium Cage 2013. SRAM Red plus WiFLi results in a win win situation for those looking for a professional level component group that provides gearing low enough to scale any climb imaginable. The heart of the WiFLi Wider Faster Lighter concept is the SRAM Red Medium Cage 10 speed rear derailleur, featuring an extended cage and a slight variation in geometry to accommodate an 11 32T cassette. Pair that with a compact crankset and you've got a wider range of gears than a triple, faster shifting on a 2x10 drivetrain, and a significant weight savings over a triple as well. All of this is replete with the smooth, quiet, precise and efficient shifts you expect from SRAM Red.